1. Field of the Invention
This invention relates to therapies for myelosuppressed patients, including aplastic anemia, anemia and thrombocytopenia. In particular, this invention relates to ex vivo activated immune cells as therapies for myelosuppressed patients. Furthermore, the invention relates to approaches to activate cells and corresponding cell culture approaches.
2. Background
Aplastic anemia is a disease characterized by ineffective hematopoiesis in a myelosuppressed patient. Patients have varying degrees of abnormalities in production of all blood cell types. Although in most cases, the cause of the disease is unknown, radiation, benzene-based compounds, viruses (e.g., hepatitis), environmental toxins, and over the counter and prescription medications have been suspected to cause myelosuppression by causing damage bone marrow, thereby leading to apoptosis of marrow stem cells. Regardless of the underlying causes, patients show similar clinical manifestations and disease progression courses. Aplastic anemia affects primarily young men and older persons of both genders. Annually, two to six per million worldwide develop this disorder, with a higher prevalence of incidences in the Orient as compared to Europe or the United States. Several causal phenomena are hypothesized for aplastic anemia: congenital, pregnancy, viral, and drugs and chemicals.
The most frequently cited causal agent of aplastic anemia is drugs or chemical exposure, which leads to the myelosuppression that underlies aplastic anemia. Some agents, such as chloramphenicol, benzene, ionizing radiation, and antineoplastic agents, cause an aplasia that is dose-related in severity from person-to-person. In these cases, marrow recovery usually occurs after withdrawal of the causal agent. Other agents, including pesticides and some anticonvulsants and antimicrobials, cause a reaction which is not dose-related and, therefore, cannot be predicted with hematological monitoring during administration. During administration of drugs, aplasias may occur even after cessation of drug therapy. In contrast to patients with idiopathic aplastic anemia, those with drug or toxin exposure exhibit similar clinical and demographic characteristics, have a similar prognosis, and a more-or-less uniform response to therapy.
In the case of benzene-induced aplastic anemia, mild to moderate disease symptoms usually disappear after patients cease being exposed to benzene. However, for patients with severe bone marrow failure or who continually need blood transfusions, effective and safe treatment has not often been heretofore available. To date, bone marrow transplantation is the only known cure.
Mild aplastic patients are often treated with as little therapy as possible. The rationale for minimum treatment for mildly aplastic patients is to remove the causal agent, thereby enabling spontaneous recovery. In young patients with severe anemia, bone marrow transplantation with an HLA-matched donor is the treatment of choice. Bone marrow transplantation effects complete remission in nearly 80% of cases. However, survival decreases to 10-20% when the donor and recipient are mismatched at two or more loci. Complications associated with transplantation include graft rejection, acute or chronic graft-versus-host disease, infection, and other miscellaneous organ specific damage. Marrow transplant recipients also have an increased long-term risk for developing subsequent solid tumors.
Indeed, bone marrow contains many of the cells involved in blood production (called hematopoiesis) and in immune function. Hematopoiesis involves many different cell types from a variety of lineages. A restoration of multiple cell lineages is useful for the effective function of the blood system. Suppression or damage to these cells can thus affect blood and/or immune function. Myelosuppression is a condition in which bone marrow cell activity is decreased, and can result in fewer red blood cells, white blood cells, and/or platelets. A pronounced shortage of white blood cells is leucopenia, and a shortage of neutrophils, which are a type of white blood cells, is termed neutropenia. Myelosuppression is probably the most common side effect of chemotherapy in cancer patients, and may lead to leucopenia, neutropenia and/or thrombocytopenia. Or various medical conditions can lead to temporary or chronic myelosuppression, which can be induced, or may result from pathophysiological conditions.
Thrombocytopenia is a condition in which the number of platelets in the blood is abnormally low, and may lead to abnormal bleeding. Thrombocytopenia purpura is a type of thrombocytopenia. Anemia and bleeding may be associated with thrombocytopenia. Severe and chronic thrombocytopenia is a complication of cancer treatment, and can be difficult to treat.
Certain growth factors have conventionally been used in attempts to treat myelosuppression, and complications such as febrile neutropenia, anemia, and bleeding, that are caused by standard-dose chemotherapy respectively. For example, factors such as G-CSF, erythropoietin and interleukin-11 have been used (James O. Armitage. Emerging Applications of Recombinant Human Granulocyte Macrophage Colony-Stimulating Factor, Blood, 92: 4491-4508, 1998; David J. Kuter and C. Glenn Begley. Recombinant human thrombopoietin: basic biology and evaluation of clinical studies. Blood, 100: 3457-3469, 2002; Xunxiang Du and David A. Williams. Interleukin-11: Review of Molecular, Cell Biology, and Clinical Use. Blood 89: 3897-3908, 1997.). However, because administration of more dose-intensive chemotherapy regimens has been pursued for better therapeutic efficacy, greater degrees of acute and prolonged myelosuppression are increasingly being observed. Severe and prolonged myelosuppression often resists the treatment of the growth factors and is managed predominantly by blood transfusion and modification of the chemotherapy dose. Moreover, thrombocytopenia associated with severe and prolonged myelosuppression is particularly difficult to treat because IL-11 (the only drug approved by FDA for treatment of chemotherapy-induced thrombocytopenia) only has a modest effect on platelet production. Thrombopoietin has been identified as a promising growth factor capable of promoting survival and maturation of megakaryocyte progenitors and platelet release in cancer patients, however, early clinical trials indicate that thrombopoietin can be antigenic in some patients, resulting in exacerbation of the disease (David J. Kuter and C. Glenn Begley. Recombinant human thrombopoietin: basic biology and evaluation of clinical studies. Blood 100, 3457-3469, 2002; Junzhi Li, Chun Yang, Yuping Xia, Amy Bertino, John Glaspy, Michael Roberts, and David J. Kuter. Thrombocytopenia caused by the development of antibodies to thrombopoietin. Blood, 98, 3241-3248, 2001.). The value of this agent in preventing and reversing severe thrombocytopenia has not been established.
Thus, while chemotherapy and radiotherapy are widely used for treatment of cancer, and as a part of procedure for bone marrow and stem cell transplantation, the efficacy of these therapies is often closely correlated with side effects; the most common side effect is myelosuppression. Mild to modest myelosuppression induced by chemotherapy and radiotherapy usually recovers either spontaneously after discontinuation of the therapy or after therapy with growth factors. But severe myelosuppression rarely recovers and often results in infection, bleeding and even death. Unfortunately, the four FDA-approved growth factors (G-CSF, GM-CSF, Interleukin-11 and Erythropoietin) that are routinely used to accelerate recovery of blood production are often not effective for severe and/or chronic myelosuppression, and the recovery of multilineage hematopoiesis.